As shown in FIG. 19, there has been known a lithium ion secondary battery 800 which includes a winding electrode assembly 801, a positive-electrode current collector terminal 802 and a negative-electrode current collector terminal 803. See JP-A-2015-41589.
The lithium ion secondary battery 800 includes: the winding electrode assembly 801; the positive-electrode current collector terminal 802 and the negative-electrode current collector terminal 803 which are connected to the winding electrode assembly 801; a battery case 804 which houses the winding electrode assembly 801; and an insulation film 805 which is disposed along an inner surface of the battery case 804. The winding electrode assembly 801 is formed by making a positive electrode sheet 808 including a positive active material layer 807 and a negative electrode sheet 810 including a negative active material layer 809 overlap with each other while interposing a separator 806 between the positive electrode sheet 808 and the negative electrode sheet 810, and by winding the positive electrode sheet 808, the negative electrode sheet 810 and the separator 806. The positive-electrode current collector terminal 802 is made of aluminum or an aluminum alloy. A distal end portion of the positive-electrode current collector terminal 802 is welded to a center portion of a positive active material layer non-forming portion 811 of the winding electrode assembly 801. The positive active material layer non-forming portion 811 is a portion of the positive electrode sheet 808 where a portion which is not coated by the positive active material layer 807 (a portion where a metal foil such as an aluminum foil is exposed) is wound. The negative-electrode current collector terminal 803 is a member made of copper or a copper alloy. A distal end portion of the negative-electrode current collector terminal 803 is welded to a center portion of a negative active material layer non-forming portion 812 of the winding electrode assembly 801. The negative active material layer non-forming portion 812 is a portion of the negative electrode sheet 810 where the portion which is not coated by the negative active material layer 809 (a portion where a metal foil such as a copper foil is exposed) is wound.
In such a lithium ion secondary battery 800, the winding electrode assembly 801 and the current collector terminals (the positive-electrode current collector terminal 802, the negative-electrode current collector terminal 803) are joined to each other by welding and hence, there may be a case where metal powder or the like generated due to welding (fine metal powder or the like generated due to joining of the winding electrode assembly 801 and the current collector terminal 802, 803) adheres to a surface of a welding portion (joint portion). In this case, when a member such as the insulation film 805 which is disposed at a position facing the welding portion is brought into contact with the welding portion during the use of the lithium ion secondary battery 800, there may be a case where the metal powder or the like is separated from the surface of the welding portion and moves to other portions.